1. Field of the Invention
The present invention relates to a power supply system and a display apparatus, and more particularly, to a power supply system having an adjustment charging value for shortening a charging period while driving a display apparatus.
2. Description of the Prior Art
During portable electronic devices rapidly developing, thinner products with energy saving and carbon reduction are much more popular in the market, and higher resolutions of a thin film transistor (TFT) liquid crystal display (LCD) is requested as well, wherein the TFT LCD having higher resolutions are equipped with more driving units for related driving operations. Due to a fixed operational period of the TFT LCD for finishing the driving operations, one TFT LCD having more driving units requests a driving period being shorter than another driving period requested by another TFT LCD having fewer driving units. Accordingly, it is an important issue to realize the circuit design with such a shorter driving period.
Besides, flexible printed circuit boards (PCBs) in the TFT LCD are installed multiple passive elements, e.g. capacitors or diodes. For the purpose of pursuing thinner and lighter products to effectively reduce the size of the flexible PCBs, these passive elements are designed to be disposed/moved inside a driving chip of the TFT LCD, and a load module corresponding to the driving chip is demonstrated as a resistor-capacitor model shown in FIG. 1A. When the load module forms as a gate type, a capacitance value is around 20 pF; when the load module forms as a source type, a capacitance value is around 30-60 pF, wherein both types of the load modules with different capacitance values correspond to a load charging period shown in FIG. 1B.
Please refer to FIG. 2A and FIG. 2B, wherein FIG. 2A illustrates a schematic diagram of a conventional two-times-voltage charging pump power supply system 2, and FIG. 2B is a schematic diagram of a charging pump module 20 in FIG. 2A. As shown in FIG. 2A and FIG. 2B, the two-times-voltage charging pump power supply system 2 comprises a charging pump module 20, an amplifying module 22 and a load module 23 (such as an equivalent load circuit of a display panel), and the charging pump module 20 comprises transistor switches M1-M8, flying capacitor units C1 and C2 and a storage capacitor unit Cs. Preferably, the charging pump module 20 utilizes conduction signals KA, KB, XA (an inversion signal of KA) and XB (an inversion signal of KB) to correspondingly conduct the transistor switches M1-M8 and utilizes a voltage VDD for charging the flying capacitor units C1 and C2, so as to output a charging voltage VS. Further, the amplifying module 22 is operated to refer to a reference voltage Vref and to amplify a voltage source, such as the charging voltage VS, to be outputted as an amplifying voltage Vout, and the amplifying voltage Vout is transmitted to the load module 24 (e.g. a display panel) to process the charging operation for the equivalent resistor-capacitor circuit.
Please refer to FIG. 2C, which illustrates a schematic diagram of a charging period of a charging pump module 20 shown in FIG. 2A. As shown in FIG. 2C, the charging pump module 20 has a regular charging period Ts and a practical charging period Tr, and the practical charging period Tr is longer than the regular charging period Ts. In other words, while the charging pump module 20 is utilized to drive the TFT LCD, a longer operational period is anticipated, such that it is difficult to provide proper circuit designs for complying with different specs of the TFT LCD.
Therefore, it has become an important issue to provide another circuit design for the conventional charging pump module, so as to make the charging pump module achieve a predetermined charging voltage within a shorter period.